Common Stock - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	1 Months Ended
	Jul. 31, 2013	Dec. 31, 2013	Dec. 31, 2012	Mar. 31, 2012
Equity [Abstract]
Shares of common stock sold in underwritten public offering	5,750,000
Public offering price	$ 5.00
Net proceeds from sale of common stock and convertible senior notes	$ 26.7
Common stock, authorized shares		200,000,000	200,000,000	200,000,000
Common stock, par value		$ 0.01	$ 0.01	$ 0.01
Common stock, issued shares		102,523,000	95,825,000
Common stock, outstanding shares		102,523,000	95,825,000